Rishi Sunak will launch his fightback in the Conservative leadership race from Margaret Thatcher’s birthplace this weekend, with his supporters urging party members to delay voting until they have seen him take on Liz Truss in more debates. Sunak’s campaign team is drawing up plans to try to reverse what one called a “worrying trend” after Truss pulled ahead by 24 percentage points in polling of party members. About 160,000 members will have the chance to decide the next prime minister when they receive ballots from 1-5 August. They can cast their votes immediately or wait until closer to the 1 September deadline. In a speech in Grantham on Saturday, the Lincolnshire home town of Thatcher, Sunak will try to move the debate on from tax cuts to the NHS by pledging to put the health service on a “war footing” with a vaccines-style taskforce set up to drive down the “emergency” of “massive backlogs”. “If we do not immediately set in train a radically different approach the NHS will come under unsustainable pressure and break,” he is expected to say. “And so from day one, I will make tackling the NHS backlog my number one public service priority.” A blitz of media appearances and visits are expected over the next fortnight, alongside a dozen hustings where the candidates will go head-to-head over the course of the six-week campaign. Sources supporting Sunak said that while party members would be able to vote from 1 August, they would be urged not to write him off until later in the contest. “We all think she [Truss] is going to be so bad at the hustings that members will change their minds,” one said. Another predicted: “He will shine at the hustings, whereas Truss is mental and will be found out.” Sunak will also stress more strongly that the Tories could lose the next election under Truss, and that he is best placed to take on Labour. To demonstrate the point, his team are said to be planning trips to “blue wall” constituencies where huge Conservative majorities were overturned in byelections, such as North Shropshire, and Tiverton and Honiton in Devon. Wary of being outflanked by Truss on personal tax cuts, Sunak’s supporters are pushing for him to directly attack the plans by arguing taxpayers’ money would be better spent on new and refurbished hospitals than on debt repayments necessary under the foreign secretary’s borrowing plans. One ally summed up the argument as: “If you bugger the economics, then there’s no way you can do all the other stuff you might want to do because you’re constantly fighting fires.” Robert Hayward, a Tory peer and elections expert, said despite the YouGov poll putting Truss ahead on 62% to Sunak’s 38% among party members, excluding those undecided, he was “not convinced” the result was a foregone conclusion. “I’m absolutely clear that the fluidity of opinion that’s been displayed by members and voters in recent weeks indicates that everything could change as a result of the debates and other political events,” he said. But Chris Hopkins, associate director of Savanta ComRes, said Sunak’s popularity with party members was “dire”. He added: “I don’t think Sunak’s resignation and perceived disloyalty to Boris [Johnson] has much to do with it, it just feels as if the membership are punishing him for his decisions he made as chancellor.” Sunak has also set his sights on getting the backing of more than half of Tory MPs. However, some of the 100-plus who backed Penny Mordaunt are reluctant to back Sunak. One said: “I would rather Rishi to Liz, but both were briefing against Penny, both either used the trans issue as a weapon or stood by and let it happen. I don’t trust either of them.” Encouraging Tory members to hold off from voting until later in the contest may also prove fruitless. “Our members are stubborn bastards,” a Sunak supporter admitted. “I can’t imagine we’ll get lots of shift.” Fraser Nelson, the editor of Spectator magazine, also predicted: “Some Tory members may dutifully wait until they have seen all 12 jousts. But most will get the voting over with quickly, then go on holiday.” Ballots in the Tory leadership race will begin to drop in members’ letterboxes from 1 to 5 August. The packs will contain a code to vote online or they can return a paper form.